Marine diffraction survey for small object detection

ABSTRACT

A seabed object detection system is provided. The system can include a receiver array. The receiver array can include a plurality of receivers disposed on a plurality of streamers. The plurality of streamers can include a central port side streamer, a central starboard side streamer, an auxiliary port side streamer and an auxiliary starboard side streamer. The system can include a source array. The source array can include a plurality of sources. The plurality of sources can include a central port side source, a central starboard side source, an auxiliary port side source, and an auxiliary port side streamer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. § 120 asa continuation of U.S. patent application Ser. No. 16/446,376, filedJun. 19, 2019, which is hereby incorporated by reference herein in itsentirety.

BACKGROUND

Seismic or other operations performed on a piece of earth can identifysubterranean characteristics or features of the analyzed piece of earth.

SUMMARY

At least one aspect of the present disclosure is directed to a seabedobject detection system which can include a receiver array. The receiverarray can include a plurality of receivers. The plurality of receiverscan receive diffraction data diffracted off an object in a seabed. Theplurality of receivers can be disposed on a plurality of streamers. Theplurality of streamers can include a central pair of streamers. Thecentral pair of streamers can include a central port side streamer and acentral starboard side streamer. The plurality of streamers can includeat least one auxiliary port side streamer located a first distance fromthe central pair of streamers. The plurality of streamers can include atleast one auxiliary starboard side streamer located a second distancefrom the central pair of streamers opposite the at least one auxiliaryport side streamer. The seabed object detection system can include asource array which can include a plurality of sources. The plurality ofsources can generate a source shot. The plurality of sources can includeat least one central pair of sources. The at least one central pair ofsources can include a central port side source and a central starboardside source. The central pair of sources can be located between thecentral pair of streamers. The plurality of sources can include at leastone auxiliary port side source. The at least one auxiliary port sidesource can be located between the central port side streamer and the atleast one auxiliary port side streamer. The plurality of sources caninclude at least one auxiliary starboard side source. The at least oneauxiliary starboard side source can be located between the centralstarboard side streamer and the at least one auxiliary starboard sidestreamer.

At least one aspect of the present disclosure is direct to a method ofseabed object detection. The method can include providing a receiverarray. The receiver array can include a plurality of receivers. Theplurality of receivers can receive diffraction data diffracted off anobject in a seabed. The plurality of receivers can be disposed on aplurality of streamers. The plurality of streamers can include a centralpair of streamers. The central pair of streamers can include a centralport side streamer and a central starboard side streamer. The pluralityof streamers can include at least one auxiliary port side streamerlocated a first distance from the central pair of streamers. Theplurality of streamers can include at least one auxiliary starboard sidestreamer located a second distance from the central pair of streamersopposite the at least one auxiliary port side streamer. The method caninclude providing a source array. The source array can include aplurality of sources. The plurality of sources can generate a sourceshot. The plurality of source can include at least one central pair ofsources. The at least one central pair of sources can include a centralport side source and a central starboard side source. The at least onecentral pair of sources can be located between the central pair ofstreamers. The plurality of sources can include at least one auxiliaryport side source. The at least one auxiliary port side source can belocated between the central port side streamer and the at least oneauxiliary port side streamer. The plurality of sources can include atleast one auxiliary starboard side source. The at least one auxiliarystarboard side source can be located between the central starboard sidestreamer and the at least one auxiliary starboard side streamer.

BRIEF DESCRIPTION OF THE DRAWINGS

The details of one or more implementations of the subject matterdescribed in this specification are set forth in the accompanyingdrawings and the description below. Other features, aspects, andadvantages of the subject matter will become apparent from thedescription, the drawings, and the claims.

FIG. 1 illustrates a seabed object detection system according to anexample implementation.

FIG. 2 illustrates a diffraction survey according to an exampleimplementation.

FIG. 3 illustrates a reflection survey according to an exampleimplementation.

FIG. 4 illustrates a seabed object detection system according to anexample implementation.

FIG. 5 illustrates a seabed object detection system according to anexample implementation.

FIG. 6 illustrates a seabed object detection system according to anexample implementation.

FIG. 7 illustrates a seabed object detection system according to anexample implementation.

FIG. 8 illustrates a seabed object detection system according to anexample implementation.

FIG. 9 illustrates a method of seabed object detection according to anexample implementation.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

Reflection-based surveys can obtain information relating to subsurfacefeatures. An acoustic signal can reflect off subsurface lithologicalformations and be acquired, analyzed and interpreted. However,reflection-based surveys typically cover a narrow area and collect asparse set of data, both of which are factors that contribute to anincreased time required to complete the surveys. Additionally, smallshallow objects such as boulders buried in the seabed may be difficultto precisely image due to the resolution capabilities ofreflection-based surveys. These small objects can complicate or delaywind turbine, marine or ocean bottom constructions that are fixed to theseabed, as well as the placement of cable connections and communicationlines between these wind turbine, marine or ocean bottom constructions.

The present disclosure is directed to systems and methods for seabedobject detection. Due to the limitations of reflection-based surveys, itcan be challenging to detect small shallow objects in the seabed.Inefficiencies related to increased survey time, such as a greater riskof weather-based delays, can increase the operating cost of thesesurveys without providing an accurate map of obstacles in the seabed.Systems and methods of the present disclosure can solve these and otherproblems associated with performing a survey to detect seabed objects.

The present disclosure is directed to systems and methods for seabedobject detection. For example, the seabed object detection system canprovide an accurate map of obstacles in the seabed. The system caninclude a receiver array. The receiver array can include a plurality ofreceivers disposed on a plurality of streamers. The plurality ofstreamers can include a central port side streamer, a central starboardside streamer, an auxiliary port side streamer and an auxiliarystarboard side streamer. The system can include a source array. Thesource array can include a plurality of sources. The plurality ofsources can include a central port side source, a central starboard sidesource, an auxiliary port side source, and an auxiliary port sidestreamer.

FIG. 1 illustrates an example seabed object detection system 100illustrative of a marine environment in which the systems and methods ofthe present disclosure can perform a seismic survey to detect seabedobjects. The seabed object detection system 100 can include a receiverarray 105. The receiver array 105 can include a plurality of receivers110. The plurality of receivers 110 can be disposed on a plurality ofstreamers 115. A streamer of the plurality of streamers 115 may be acable (e.g., a surface marine cable), an assembly of wires, or anycomponent capable of connecting a receiver to a recording device whichmay be located on a vessel 102. The receiver array 105 can include oneor more receivers. For example, the receiver array 105 can include aplurality of receivers 110 coupled to a plurality of streamers 115. Thereceiver array 105 can include a pattern of receivers. For example, theplurality of receivers 110 can be coupled to the plurality of streamers115 along a line. The plurality of receivers 110 of the receiver array105 can be coupled to the plurality of streamers 115 in a grid pattern.The receiver array 105 can be the pattern formed by the plurality ofreceivers 110 disposed on the plurality of streamers 115. For example,the receiver array 105 can include a plurality of receivers 110 disposedalong a streamer of the plurality of streamers 115. The receiver array105 can include a plurality of receivers 110 disposed on multiplestreamers of the plurality of streamers 115. The receiver array 105 canreceive diffraction data diffracted off an object in the seabed.

The receiver array 105 can include a plurality of receivers 110. Theplurality of receivers 110 can receive diffraction data diffracted offan object in a seabed. For example, a receiver of the plurality ofreceivers 110 may be a hydrophone or any other device capable ofcollecting seismic data. Seismic data can include reflection dataindicating subsurface features of the seabed. Seismic data can includediffraction data indicating subsurface features of the seabed. Thesubsurface features of the seabed can include small shallow objects suchas boulders. The small shallow objects can be between 10 cm and 100 cmwide (e.g., 20 cm, 30 cm, 40 cm, 50 cm, 60 cm, 70 cm, 80 cm, 90 cm, 100cm). The small shallow objects can be greater than 100 cm. These smallshallow objects can be less than 10 cm. The plurality of receivers 110can be configured to detect acoustic waves that are reflected by seabedobjects. The plurality of receivers 110 can be configured to detectacoustic waves that are diffracted by seabed objects. The plurality ofreceivers 110 can detect diffraction data from edges of objects. Forexample, the plurality of receivers 110 can detect diffraction dataoriginating from edges of large objects. The large objects can have avolume of between 100 and 500 cubic meters (e.g., 100 cubic meters, 200cubic meters, 300 cubic meters, 400 cubic meters, 500 cubic meters). Thelarge objects can have a volume of less than 100 cubic meters. The largeobjects can have a volume of greater than 100 cubic meters. The largeobject can be a shipping container. The diffraction data can originatefrom corners of the shipping container. The plurality of receivers 110can detect objects with irregular surface features. For example, theplurality of receivers 110 can detect objects with facets, edges, sharpboundaries, or textures. The seabed objects can be completely buriedwithin the seabed. The seabed objects can be partially buried within theseabed.

The plurality of streamers 115 can include a central pair of streamers.The central pair of streamers can include a central port side streamer125 and a central starboard side streamer 130. The central port sidestreamer 125 may be a cable (e.g., a surface marine cable), an assemblyof wires, or any component capable of connecting a receiver to arecording device which may be located on the vessel 102. The recordingdevice can receive data, such as reflection and diffraction data, fromthe plurality of receivers 110 disposed on the plurality of streamers115. The central port side streamer 125 may be disposed on a port sideof the vessel 102. The central starboard side streamer 130 may be acable (e.g., a surface marine cable), an assembly of wires, or anycomponent capable of connecting a receiver to a recording device whichmay be located on the vessel 102. The central starboard side streamer130 may be disposed on a starboard side of the vessel 102.

The plurality of streamers 115 can include an auxiliary port sidestreamer 135. The auxiliary port side streamer 135 can be located afirst distance from the central pair of streamers. For example, theauxiliary port side streamer 135 can be located a first distance fromthe central port side streamer 125. The auxiliary port side streamer 135can be located a first distance from the central starboard side streamer130. The first distance can include distances between about 5 meters and30 meters. For example, the first distance can be 12.5 meters. The firstdistance can be less than 5 meters. The first distance can be greaterthan 30 meters. The auxiliary port side streamer 135 may be a cable(e.g., a surface marine cable), an assembly of wires, or any componentcapable of connecting a receiver to a recording device which may belocated on the vessel 102. The auxiliary port side streamer 135 may bedisposed on a port side of the vessel 102. The plurality of streamers115 can include multiple auxiliary port side streamers 135. For example,the plurality of streamers 115 can include one, two, three, or moreauxiliary port side streamers 135.

The plurality of streamers 115 can include an auxiliary starboard sidestreamer 140. The auxiliary starboard side streamer 140 can be located asecond distance from the central pair of streamers. For example, theauxiliary starboard side streamer 140 can be located a second distancefrom the central port side streamer 125. The auxiliary starboard sidestreamer 140 can be located a second distance from the central starboardside streamer 130. The second distance can include distances betweenabout 5 meters and 30 meters. For example, the second distance can be12.5 meters. The second distance can be less than 5 meters. The seconddistance can be greater than 30 meters. The second distance can beapproximately the same as the first distance. The auxiliary starboardside streamer 140 may be a cable (e.g., a surface marine cable), anassembly of wires, or any component capable of connecting a receiver toa recording device which may be located on the vessel 102. The auxiliarystarboard side streamer 140 may be disposed on a starboard side of thevessel 102. The auxiliary starboard side streamer 140 can be locatedopposite the auxiliary port side streamer 135. The plurality ofstreamers 115 can include multiple auxiliary starboard side streamers140. For example, the plurality of streamers 115 can include one, two,three, or more auxiliary starboard side streamers 140. The plurality ofstreamers 115 can include exactly eight streamers. For example, theplurality of streamers 115 can include one central port side streamer125, one central starboard side streamer 130, three auxiliary port sidestreamers 135, and three auxiliary starboard side streamers 140.

The seabed object detection system 100 can include a source array 127.The source array 127 can include a plurality of sources. The pluralityof sources can include a central port side source 150, a centralstarboard side source 155, an auxiliary port side source 160, and anauxiliary starboard side source 165. A source of the plurality ofsources can generate a source shot. A source of the plurality of sourcescan generate acoustic waves. The source array 127 can generate anacoustic signal to be received by the receiver array 105. For example,the source array 127 can include a plurality of sources coupled to asource cable 197. The source array can include a pattern of sources. Thesources can include a central port side source 150, a central starboardside source 155, an auxiliary port side source 160, and an auxiliarystarboard side source 165. For example, the central port side source150, the central starboard side source 155, the auxiliary port sidesource 160, and the auxiliary starboard side source 165 can be coupledto the source cable 197 to form a source array 127.

The source array 127 can include at least one central pair of sources.The source array 127 can include a central pair of sources. The centralpair of sources can include a central port side source 150 and a centralstarboard side source 155. The central pair of sources can be locatedbetween the central pair of streamers. For example, the central portside source 150 can be located between the central port side streamer125 and the central starboard side streamer 130. The central port sidesource 150 can generate a source shot. The central port side source 150can generate acoustic waves. The central port side source 150 cangenerate acoustic waves to be reflected off a seabed object and receivedby the plurality of receivers 110. The central port side source 150 cangenerate acoustic waves to be diffracted off a seabed object andreceived by the plurality of receivers 110. The central starboard sidesource 155 can be located between the central port side streamer 125 andthe central starboard side streamer 130. The central starboard sidesource 155 can generate a source shot. The central starboard side source155 can generate acoustic waves. The central starboard side source 155can generate acoustic waves to be reflected off a seabed object andreceived by the plurality of receivers 110. The central starboard sidesource 155 can generate acoustic waves to be diffracted off a seabedobject and received by the plurality of receivers 110.

The source array 127 can include at least one auxiliary port side source160. The source array can include an auxiliary port side source 160. Theauxiliary port side source 160 can be located between the central portside streamer 125 and the auxiliary port side streamer 135. Theauxiliary port side source 160 can be located between a first auxiliaryport side streamer 135 and a second auxiliary port side streamer 135.The auxiliary port side source 160 can generate a source shot. Theauxiliary port side source 160 can generate acoustic waves. Theauxiliary port side source 160 can generate acoustic waves to bereflected off a seabed object and received by the plurality of receivers110. The auxiliary port side source 160 can generate acoustic waves tobe diffracted off a seabed object and received by the plurality ofreceivers 110. The source array 127 can include multiple auxiliary portside sources 160. For example, the source array 127 can include one,two, three, or more auxiliary port side sources 160.

The source array 127 can include at least one auxiliary starboard sidesource 165. The auxiliary starboard side source 165 can be locatedbetween the central starboard side streamer 130 and the auxiliarystarboard side streamer 140. The auxiliary starboard side source 165 canbe located between a first auxiliary starboard side streamer 140 and asecond auxiliary starboard side streamer 140. The auxiliary starboardside source 165 can generate a source shot. The auxiliary starboard sidesource 165 can generate acoustic waves. The auxiliary starboard sidesource 165 can generate acoustic waves to be reflected off a seabedobject and received by the plurality of receivers 110. The auxiliarystarboard side source 165 can generate acoustic waves to be diffractedoff a seabed object and received by the plurality of receivers 110. Thesource array 127 can include multiple auxiliary starboard side source165. For example, the source array 127 can include one, two, three, ormore auxiliary starboard side source 165. The plurality of sources caninclude exactly eight sources. For example, the plurality of sources caninclude one central port side source 150, one central starboard sidesource 155, three auxiliary port side sources 160, and three auxiliarystarboard side sources 165.

The seabed object detection system 100 can include a port side diverter170. The port side diverter 170 may be a diverter, a paravane ordeflecting plate that redirects the motion of water past the diverterlaterally to produce an amount of lateral force. The diverter can beconfigured to redirect flow of water past the diverter with respect to adirection of motion of the diverter through water. The diverter caninclude a steering device associated with the diverter. The steeringdevice can redirect the flow of water to control an amount of lateralforce generated by the diverter. The port side diverter 170 can beconnected by a cable to a starboard side diverter 175. The cable caninclude a streamer cable 195. For example, the port side diverter 170can be directed connected or coupled to the streamer cable 195. The portside diverter 170 can be connected or coupled to the streamer cable 195by a coupling device or a secondary cable. The coupling device cancouple the port side diverter 170 to the streamer cable 195. Thestreamer cable 195 can be connected to the plurality of streamers 115.The plurality of streamers 115 can be connected or coupled to thestreamer cable 195 by a coupling device or a secondary cable. Thecoupling device can couple the streamer cable 195 to the plurality ofstreamers 115.

The seabed object detection system 100 can include a starboard sidediverter 175. The starboard side diverter 175 may be a diverter, aparavane or deflecting plate that redirects the motion of water past thediverter laterally to produce an amount of lateral force. The divertercan be configured to redirect flow of water past the diverter withrespect to a direction of motion of the diverter through water. Thediverter can include a steering device associated with the diverter. Thesteering device can redirect the flow of water to control an amount oflateral force generated by the diverter. The starboard side diverter 175can be connected by a cable to a port side diverter 170. The cable caninclude a streamer cable 195. For example, the starboard side diverter175 can be directed connected or coupled to the streamer cable 195. Thestarboard side diverter 175 can be connected or coupled to the streamercable 195 by a coupling device or a secondary cable. The coupling devicecan couple the starboard side diverter 175 to the streamer cable 195.The streamer cable 195 can be connected to the plurality of streamers115. The plurality of streamers 115 can be connected or coupled to thestreamer cable 195 by a coupling device or a secondary cable. Thecoupling device can couple the streamer cable 195 to the plurality ofstreamers 115.

The seabed object detection system 100 can include a vessel 102. Thevessel 102 can tow the receiver array 105. The vessel 102 can tow thesource array 127. The vessel 102 can tow the source array 127 ahead ofthe receiver array 105. The vessel 102 can be connected to the port sidediverter 170. The vessel 102 can be connected to the port side diverter170 by a port side cable 180. The vessel 102 can be coupled to the portside diverter 170. The vessel 102 can be coupled to the port sidediverter 170 by the port side cable 180. The port side cable 180 may bea surface marine cable, an assembly of wires, or any component capableof connecting a receiver to a recording device which may be located onthe vessel 102. The port side cable 180 may be a power cable to transmitelectrical power from the vessel 102 to the plurality of sources or theplurality of receivers 110. The vessel 102 can be connected to thestarboard side diverter 175. The vessel 102 can be connected to thestarboard side diverter 175 by a starboard side cable 185. The vessel102 can be coupled to the starboard side diverter 175. The vessel 102can be coupled to the starboard side diverter 175 by the starboard sidecable 185. The starboard side cable 185 may be a surface marine cable,an assembly of wires, or any component capable of connecting a receiverto a recording device which may be located on the vessel 102. Thestarboard side cable 185 may be a power cable to transmit electricalpower from the vessel 102 to the plurality of sources or the pluralityof receivers 110. The vessel 102 can tow the receiver array 105 and thesource array 127 such that the receiver array 105 receives diffractiondata diffracted off an object in the seabed. The diffraction datadiffracted off the object in the seabed can include diffracted wavesgenerated by the source array 127. The source array 127 can generate anacoustic signals to diffract off the object in the seabed.

The seabed object detection system 100 can include a streamer cable 195.The streamer cable 195 can connect the port side diverter 170 to thestarboard side diverter 175. The streamer cable may be a surface marinecable, an assembly of wires, or any component capable of connecting areceiver to a recording device which may be located on the vessel 102.The streamer cable 195 can be coupled to the port side diverter 170. Thestreamer cable 195 can be coupled to the starboard side diverter 175.The streamer cable 195 can be multiple cables. For example, the streamercable 195 can be multiple cables coupled together to form a longercable. The streamer cable 195 can be connected to the central port sidestreamer 125. The streamer cable 195 can be connected to the centralstarboard side streamer 130. The streamer cable 195 can be connected tothe auxiliary port side streamer 135. The streamer cable 195 can beconnected to the auxiliary starboard side streamer 140.

The streamer cable 195 can be a power cable to transmit electrical powerfrom the vessel 102 to the plurality of receivers 110. The streamercable 195 can transmit electrical power from the vessel 102 to areceiver disposed on the central port side streamer 125. The streamercable 195 can transmit electrical power from the vessel 102 to areceiver disposed on the central starboard side streamer 130. Thestreamer cable 195 can transmit electrical power from the vessel 102 toa receiver disposed on the auxiliary port side streamer 135. Thestreamer cable 195 can transmit electrical power from the vessel 102 toa receiver disposed on the auxiliary starboard side streamer 140.

The seabed object detection system 100 can include a source cable 197.The source cable 197 can connect the port side cable 180 to thestarboard side cable 185. The source cable 197 can couple to the portside cable 180 at a point closer to the port side diverter 170 than tothe vessel 102. The source cable 197 can couple to the starboard sidecable 185 at a point closer to the starboard side diverter 175 than tothe vessel 102. The source cable 197 can be directly connected orcoupled to the port side cable 180. The source cable 197 can be directlyconnected or coupled to the starboard side cable 185. The source cable197 can be connected to the source array 127. The source cable 197 canbe directly connected or coupled to the source array 127. The sourcecable 197 can be connected to the central port side source 150. Thesource cable 197 can be connected to the central starboard side source155. The source cable 197 can be connected to the auxiliary port sidesource 160. The source cable 197 can be connected to the auxiliarystarboard side source 165. The source cable 197 can be connected to thecentral port side source 150 through a secondary cable. The source cable197 can be connected to the central starboard side source 155 through asecondary cable. The source cable 197 can be connected to the auxiliaryport side source 160 through a secondary cable. The source cable 197 canbe connected to the auxiliary starboard side source 165 through asecondary cable.

The source cable 197 can be a power cable to transmit electrical powerfrom the vessel 102 to the plurality of sources. The source cable 197can transmit electrical power from the vessel 102 to the central portside source 150. The source cable 197 can transmit electrical power fromthe vessel 102 to the central starboard side source 155. The sourcecable 197 can transmit electrical power from the vessel 102 to theauxiliary port side source 160. The source cable 197 can transmitelectrical power from the vessel 102 to the auxiliary starboard sidesource 165.

The seabed object detection system 100 can include a plurality of powercables 190. The power cable 190 can include an electrical cable totransmit electrical power. The power cable 190 can transmit electricalpower from the vessel 102 to the plurality of sources of the sourcearray 127. The power cable 190 can transmit electrical power from thevessel 102 to the central port side source 150. The power cable 190 cantransmit electrical power from the vessel 102 to the central starboardside source 155. The power cable 190 can transmit electrical power fromthe vessel 102 to the auxiliary port side source 160. The power cable190 can transmit electrical power from the vessel 102 to the auxiliarystarboard side source 165.

FIG. 2 illustrates a diffraction survey 200. The diffraction survey 200can include a receiver array 105 and a source array 127. The sourcearray 127 can generate a source shot 215. The source shot 215 can travelthrough a medium (e.g., sea water) and diffract off a seabed object 210.The seabed object 210 can be completed buried in the seabed 220. Theseabed object 210 can be partially buried in the seabed 220. The seabedobject 210 can include small shallow objects such as boulders. The smallshallow objects can be between 10 cm and 100 cm wide (e.g., 20 cm, 30cm, 40 cm, 50 cm, 60 cm, 70 cm, 80 cm, 90 cm, 100 cm). The small shallowobjects can be greater than 100 cm. These small shallow objects can beless than 10 cm. The waves that diffract off the seabed object 210 mayinclude diffraction data. The diffraction data may include diffractedwaves 205. The receiver array 105 can receive diffraction data. Forexample, the receiver array 105 can receive the diffracted waves 205.The plurality of receivers 110 of the receiver array 105 can receivediffraction data. For example, the plurality of receivers 110 canreceive the diffracted waves 205. A receiver of the plurality ofreceivers 110 can receive the diffracted waves 205. The diffraction datacan include diffracted waves 205 originating from a seabed object. Thediffraction data can include diffracted waves 205 generated from asource shot 215. The plurality of receivers 110 can detect diffractiondata from edges of objects. For example, the plurality of receivers 110can detect diffraction data originating from edges of large objects. Thelarge objects can have a volume of between 100 and 500 cubic meters(e.g., 100 cubic meters, 200 cubic meters, 300 cubic meters, 400 cubicmeters, 500 cubic meters). The large objects can have a volume of lessthan 100 cubic meters. The large objects can have a volume of greaterthan 100 cubic meters. The large object can be a shipping container. Thediffraction data can originate from corners of the shipping container.The plurality of receivers 110 can detect objects with irregular surfacefeatures. For example, the plurality of receivers 110 can detect objectswith facets, edges, sharp boundaries, or textures.

The plurality of receivers 110 of the receiver array 105 can receivediffraction data. The diffraction data can include diffracted waves 205diffracted off a seabed object that is smaller than a Fresnel zone. TheFresnel zone is an area of a reflected from which most of the energy ofa reflection is returned and arrival times of the reflection differ byless than half a period from an arrival of energy propagated from anenergy source. Waves with such arrival times may interfereconstructively and be detected by a single arrival. Therefore, detectingreflection waves from an object smaller than the Fresnel zone may bedifficult. However, the plurality of receivers 110 of the receiver array105 can detect diffracted waves from an object smaller than the Fresnelzone.

The source array 127 can generate acoustic waves. The acoustic waves caninclude a source shot 215. The acoustic waves can diffract off theobject in the seabed. The receiver array 105 can receive diffractedwaves originating from the object in the seabed. The central pair ofsources can generate acoustic waves. The central port side source 150can generate acoustic waves. The central starboard side source 155 cangenerate acoustic waves. The auxiliary port side source 160 can generateacoustic waves. The auxiliary starboard side source 165 can generateacoustic waves. A receiver of the plurality of receivers 110 of thereceiver array 105 can receive the diffracted waves. A receiver disposedon the central port side streamer 125 can receive the diffracted waves.A receiver disposed on the central starboard side streamer 130 canreceive the diffracted waves. A receiver disposed on the auxiliary portside streamer 135 can receive the diffracted waves. A receiver disposedon the auxiliary starboard side streamer 140 can receive the diffractedwaves.

FIG. 3 illustrates a reflection survey 300. The reflection survey 300can include a receiver array 105 and a source array 127. The sourcearray 127 can generate a source shot 215. The source shot 215 can travelthrough a medium (e.g., sea water) and reflect off a seabed object 210.The seabed object 210 can be completed buried in the seabed 220. Theseabed object 210 can be partially buried in the seabed 220. The seabedobject 210 can include small shallow objects such as boulders. The smallshallow objects can be between 10 cm and 100 cm wide (e.g., 20 cm, 30cm, 40 cm, 50 cm, 60 cm, 70 cm, 80 cm, 90 cm, 100 cm). The small shallowobjects can be greater than 100 cm. These small shallow objects can beless than 10 cm. The waves that reflect off the seabed object 210 mayinclude reflection data. The reflection data may include a reflectedwave 305. The receiver array 105 can receive reflection data. Forexample, the receiver array 105 can receive the reflected wave 305. Areceiver of the plurality of receivers 110 can receive the reflectedwave 305. The reflection data can include a reflected wave 305originating from a seabed object. The reflection data can include thereflected wave 305 generated from a source shot 215. The plurality ofsources of the source array 127 can generate an acoustic signal. Theplurality of receivers 110 of the receiver array 105 can receivereflection data reflected off the object in the seabed. The reflectiondata can include a reflected wave 305. A receiver of the plurality ofreceivers 110 can receive the reflected wave 305 reflected off theobject in the seabed and generated by a source of the plurality ofsources of the source array 127.

FIG. 4 illustrates a seabed object detection system 100. The seabedobject detection system 100 can include a source array 127 and areceiver array 105. The source array 127 can generate a first sourceshot 405. The source array 127 can generate a second source shot 415.The source array 127 can generate a third source shot 425. The firstsource shot 405 can reflect off the seabed 220 at an angle, θ₁ 440. Thereceiver array 105 can receive the wave reflected off the seabed 220 atan angle, θ₁ 440. A receiver of the plurality of receivers 110 canreceive the wave reflected off the seabed 220 at an angle, θ₁ 440. Thewave reflected off the seabed 220 can be a reflected wave 410. Theangle, θ₁ 440 can be less than a critical angle of reflection for asource of the source array 127.

The second source shot 415 can reflect off the seabed 220 at an angle,θ₂ 445. For example, the angle, θ₂ 445 can be a critical angle ofreflection for the source of the source array 127. Instead of a wavereflected off the seabed 220, a refracted wave 420 is generated from thesecond source shot 415. The critical angle can include a critical angleof reflection. The critical angle can include a critical angle ofincidence. The critical angle of incidence is the angle at which arefracted wave travels along an interface between two media. Thecritical angle can depend on a distance 435 between the seabed 220 andthe receiver array 105. The distance 435 can be between 10 m and 100meters. For example, the distance can be 15 m, 25 m, 50 m, or 75 m. Thedistance 435 can be less than 10 m. The distance 435 can be greater than100 meters. The receiver array 105 does not receive a wave reflected offthe seabed 220 at an angle, θ₂ 445. A receiver of the plurality ofreceivers 110 does not receive a wave reflected off the seabed 220 at anangle, θ₂ 445. A receiver of the plurality of receivers 110 can bedisposed at a critical angle of reflection for a source of the sourcearray 127. A receiver of the plurality of receivers 110 can be disposedat a critical angle of reflection for a source of the plurality ofsources of the source array 127. The receiver disposed at a criticalangle of reflection can receive diffraction data responsive to anacoustic source. The receiver disposed at a critical angle of reflectioncan receive diffraction data generated from the second source shot 415.The second source shot 415 can generate acoustic waves. The receiverdisposed at a critical angle of reflection can receive diffraction datagenerated from the acoustic waves.

The third source shot 425 can reflect off the seabed 220 at an angle, θ₃450. For example, the angle, θ₃ 450 can be greater than a critical angleof reflection for the source of the source array 127. Instead of a wavereflected off the seabed 220, a refracted wave 430 is generated from thethird source shot 425. The receiver array 105 does not receive a wavereflected off the seabed 220 at an angle, θ₃ 450. A receiver of theplurality of receivers 110 does not receive a wave reflected off theseabed 220 at an angle, θ₃ 450. A receiver of the plurality of receivers110 can be disposed beyond a critical angle of reflection for a sourceof the source array 127. A receiver of the plurality of receivers 110can be disposed beyond a critical angle of reflection for a source ofthe plurality of sources of the source array 127. The receiver disposedbeyond a critical angle of reflection can receive diffraction dataresponsive to an acoustic source. The receiver disposed beyond acritical angle of reflection can receive diffraction data generated fromthe third source shot 425. The third source shot 425 can generateacoustic waves. The receiver disposed beyond a critical angle ofreflection can receive diffraction data generated from the acousticwaves.

The receiver array 105 can be disposed a distance 435 above the seabed220. For example, the receiver array 105 can be disposed 15 m to 50 mabove the seabed (e.g., 15 m, 25 m, 40 m, 50 m). The receiver array 105can be disposed at a distance 435 less than 15 m above the seabed. Thereceiver array 105 can be disposed at a distance 435 greater than 50meters above the seabed. The plurality of receivers 110 of the receiverarray 105 can be disposed a distance 435 above the seabed 220. Eachreceiver of the plurality of receivers 110 can be disposed at thesubstantially the same distance 435 above the seabed 220. The receiverarray 105 can be disposed a distance below the sea surface. Theplurality of receivers 110 of the receiver array 105 can be disposed adistance below the sea surface. The source array 127 can be disposed adistance above the seabed 220. For example, the source array 127 can bedisposed 15 m to 50 m above the seabed. The receiver array 105 can betowed deeper than the source array 127.

FIG. 5 illustrates a seabed object detection system 100. The seabedobject detection system 100 can include an auxiliary port side source160. For example, the auxiliary port side source 160 can be locatedbetween the central port side streamer 125 and a midline 505 of thecentral port side streamer 125 and an auxiliary port side streamer 135.The auxiliary port side source 160 can be located on a midline 505 ofthe central port side streamer 125 and an auxiliary port side streamer135. The auxiliary port side source 160 can be located between a firstauxiliary port side streamer 135 and a second auxiliary port sidestreamer 135. The auxiliary port side source 160 can be located betweena first auxiliary port side streamer 135 and a midline 505 of the firstauxiliary port side streamer 135 and the second auxiliary port sidestreamer 135. The auxiliary port side source 160 can be located betweena second auxiliary port side streamer 135 and a third auxiliary portside streamer 135. The auxiliary port side source 160 can be locatedbetween a second auxiliary port side streamer 135 and a midline 505 ofthe second auxiliary port side streamer 135 and the third auxiliary portside streamer 135.

The seabed object detection system 100 can include an auxiliarystarboard side source 165. For example, the auxiliary starboard sidesource 165 can be located between the central starboard side streamer130 and a midline 505 of the central port side streamer 125 and anauxiliary port side streamer 135. The auxiliary starboard side source165 can be located on a midline 510 of the central starboard sidestreamer 130 and an auxiliary starboard side streamer 140. The auxiliarystarboard side source 165 can be located between a first auxiliarystarboard side streamer 140 and a second auxiliary starboard sidestreamer 140. The auxiliary starboard side source 165 can be locatedbetween a first auxiliary starboard side streamer 140 and a midline 515of the first auxiliary starboard side streamer 140 and the secondauxiliary starboard side streamer 140. The auxiliary starboard sidesource 165 can be located between a second auxiliary starboard sidestreamer 140 and a third auxiliary starboard side streamer 140. Theauxiliary starboard side source 165 can be located between a secondauxiliary starboard side streamer 140 and a midline 515 of the secondauxiliary starboard side streamer 140 and the third auxiliary starboardside streamer 140.

FIG. 6 illustrates a seabed object detection system 100. The seabedobject detection system 100 can include a receiver array 105. Thereceiver array 105 can include a plurality of receivers 110. Theplurality of receivers 110 can be disposed on a plurality of streamers115. A streamer of the plurality of streamers 115 may be a cable (e.g.,a surface marine cable), an assembly of wires, or any component capableof connecting a receiver to a recording device which may be located on avessel 102. The receiver array 105 can include one or more receivers.For example, the receiver array 105 can include a plurality of receivers110 coupled to a plurality of streamers 115. The receiver array 105 caninclude a pattern of receivers. For example, the plurality of receivers110 can be coupled to the plurality of streamers 115 along a line. Theplurality of receivers 110 of the receiver array 105 can be coupled tothe plurality of streamers 115 in a grid pattern. The receiver array 105can be the pattern formed by the plurality of receivers 110 disposed onthe plurality of streamers 115. For example, the receiver array 105 caninclude a plurality of receivers 110 disposed along a streamer of theplurality of streamers 115. The receiver array 105 can include aplurality of receivers 110 disposed on multiple streamers of theplurality of streamers 115. The receiver array 105 can receivediffraction data diffracted off an object in the seabed.

The receiver array 105 can include a plurality of receivers 110. Theplurality of receivers 110 can receive diffraction data diffracted offan object in a seabed. For example, a receiver of the plurality ofreceivers 110 may be a hydrophone or any other device capable ofcollecting seismic data. Seismic data can include reflection dataindicating subsurface features of the seabed. Seismic data can includediffraction data indicating subsurface features of the seabed. Thesubsurface features of the seabed can include small shallow objects suchas boulders. The small shallow objects can be between 10 cm and 100 cmwide (e.g., 20 cm, 30 cm, 40 cm, 50 cm, 60 cm, 70 cm, 80 cm, 90 cm, 100cm). The small shallow objects can be greater than 100 cm. These smallshallow objects can be less than 10 cm. The plurality of receivers 110can be configured to detect acoustic waves that are reflected by seabedobjects. The plurality of receivers 110 can be configured to detectacoustic waves that are diffracted by seabed objects. The plurality ofreceivers 110 can detect diffraction data from edges of objects. Forexample, the plurality of receivers 110 can detect diffraction dataoriginating from edges of large objects. The large objects can have avolume of between 100 and 500 cubic meters (e.g., 100 cubic meters, 200cubic meters, 300 cubic meters, 400 cubic meters, 500 cubic meters). Thelarge objects can have a volume of less than 100 cubic meters. The largeobjects can have a volume of greater than 100 cubic meters. The largeobject can be a shipping container. The diffraction data can originatefrom corners of the shipping container. The plurality of receivers 110can detect objects with irregular surface features. For example, theplurality of receivers 110 can detect objects with facets, edges, sharpboundaries, or textures. The seabed objects can be completely buriedwithin the seabed. The seabed objects can be partially buried within theseabed.

The plurality of streamers 115 can include a central pair of streamers.The central pair of streamers can include a central port side streamer125 and a central starboard side streamer 130. The central port sidestreamer 125 may be a cable (e.g., a surface marine cable), an assemblyof wires, or any component capable of connecting a receiver to arecording device which may be located on the vessel 102. The recordingdevice can receive data, such as reflection and diffraction data, fromthe plurality of receivers 110 disposed on the plurality of streamers115. The central port side streamer 125 may be disposed on a port sideof the vessel 102. The central starboard side streamer 130 may be acable (e.g., a surface marine cable), an assembly of wires, or anycomponent capable of connecting a receiver to a recording device whichmay be located on the vessel 102. The central starboard side streamer130 may be disposed on a starboard side of the vessel 102.

The plurality of streamers 115 can include an auxiliary port sidestreamer 135. The auxiliary port side streamer 135 can be located afirst distance from the central pair of streamers. For example, theauxiliary port side streamer 135 can be located a first distance fromthe central port side streamer 125. The auxiliary port side streamer 135can be located a first distance from the central starboard side streamer130. The first distance can include distances between about 5 meters and30 meters. For example, the first distance can be 12.5 meters. The firstdistance can be less than 5 meters. The first distance can be greaterthan 30 meters. The auxiliary port side streamer 135 may be a cable(e.g., a surface marine cable), an assembly of wires, or any componentcapable of connecting a receiver to a recording device which may belocated on the vessel 102. The auxiliary port side streamer 135 may bedisposed on a port side of the vessel 102. The plurality of streamers115 can include multiple auxiliary port side streamers 135. For example,the plurality of streamers 115 can include one, two, three, four, five,six, seven or more auxiliary port side streamers 135.

The plurality of streamers 115 can include an auxiliary starboard sidestreamer 140. The auxiliary starboard side streamer 140 can be located asecond distance from the central pair of streamers. For example, theauxiliary starboard side streamer 140 can be located a second distancefrom the central port side streamer 125. The auxiliary starboard sidestreamer 140 can be located a second distance from the central starboardside streamer 130. The second distance can include distances betweenabout 5 meters and 30 meters. For example, the second distance can be12.5 meters. The second distance can be less than 5 meters. The seconddistance can be greater than 30 meters. The second distance can beapproximately the same as the first distance. The auxiliary starboardside streamer 140 may be a cable (e.g., a surface marine cable), anassembly of wires, or any component capable of connecting a receiver toa recording device which may be located on the vessel 102. The auxiliarystarboard side streamer 140 may be disposed on a starboard side of thevessel 102. The auxiliary starboard side streamer 140 can be locatedopposite the auxiliary port side streamer 135. The plurality ofstreamers 115 can include multiple auxiliary starboard side streamers140. For example, the plurality of streamers 115 can include one, two,three, four, five, six, seven or more auxiliary starboard side streamers140. The plurality of streamers 115 can include exactly sixteenstreamers. For example, the plurality of streamers 115 can include onecentral port side streamer 125, one central starboard side streamer 130,seven auxiliary port side streamers 135, and seven auxiliary starboardside streamers 140.

The seabed object detection system 100 can include a port side diverter170. The port side diverter 170 may be a diverter, a paravane ordeflecting plate that redirects the motion of water past the diverterlaterally to produce an amount of lateral force. The diverter can beconfigured to redirect flow of water past the diverter with respect to adirection of motion of the diverter through water. The diverter caninclude a steering device associated with the diverter. The steeringdevice can redirect the flow of water to control an amount of lateralforce generated by the diverter. The port side diverter 170 can beconnected by a cable to a starboard side diverter 175. The cable caninclude a streamer cable 195. For example, the port side diverter 170can be directed connected or coupled to the streamer cable 195. The portside diverter 170 can be connected or coupled to the streamer cable 195by a coupling device or a secondary cable. The coupling device cancouple the port side diverter 170 to the streamer cable 195. Thestreamer cable 195 can be connected to the plurality of streamers 115.The plurality of streamers 115 can be connected or coupled to thestreamer cable 195 by a coupling device or a secondary cable. Thecoupling device can couple the streamer cable 195 to the plurality ofstreamers 115. The plurality of streamers 115 can be coupled to thestreamer cable 195 across substantially the entire length of thestreamer cable 195.

The seabed object detection system 100 can include a starboard sidediverter 175. The starboard side diverter 175 may be a diverter, aparavane or deflecting plate that redirects the motion of water past thediverter laterally to produce an amount of lateral force. The divertercan be configured to redirect flow of water past the diverter withrespect to a direction of motion of the diverter through water. Thediverter can include a steering device associated with the diverter. Thesteering device can redirect the flow of water to control an amount oflateral force generated by the diverter. The starboard side diverter 175can be connected by a cable to a port side diverter 170. The cable caninclude a streamer cable 195. For example, the starboard side diverter175 can be directed connected or coupled to the streamer cable 195. Thestarboard side diverter 175 can be connected or coupled to the streamercable 195 by a coupling device or a secondary cable. The coupling devicecan couple the starboard side diverter 175 to the streamer cable 195.The streamer cable 195 can be connected to the plurality of streamers115. The plurality of streamers 115 can be connected or coupled to thestreamer cable 195 by a coupling device or a secondary cable. Thecoupling device can couple the streamer cable 195 to the plurality ofstreamers 115. The plurality of streamers 115 can be coupled to thestreamer cable 195 across substantially the entire length of thestreamer cable 195.

FIG. 7 illustrates a seabed object detection system 100. The seabedobject detection system 100 can include a source array 127. The sourcearray 127 can include a plurality of sources. The plurality of sourcescan include a central port side source 150, a central starboard sidesource 155, an auxiliary port side source 160, and an auxiliarystarboard side source 165. A source of the plurality of sources cangenerate a source shot. A source of the plurality of sources cangenerate acoustic waves. The source array 127 can generate an acousticsignal to be received by the receiver array 105. For example, the sourcearray 127 can include a plurality of sources coupled to a source cable197. The source array can include a pattern of sources. The sources caninclude a central port side source 150, a central starboard side source155, an auxiliary port side source 160, and an auxiliary starboard sidesource 165. For example, the central port side source 150, the centralstarboard side source 155, the auxiliary port side source 160, and theauxiliary starboard side source 165 can be coupled to the source cable197 to form a source array 127. The source array 127 can include sixteensources. For example, the plurality of sources can include one centralport side source 150 including two sources, one central starboard sidesource 155 including two sources, three auxiliary port side sources 160each including two sources, and three auxiliary starboard side sources165 each including two sources.

The source array 127 can include at least one central pair of sources.The source array 127 can include a central pair of sources. The centralpair of sources can include a central port side source 150 and a centralstarboard side source 155. The central pair of sources can be locatedbetween the central pair of streamers. For example, the central portside source 150 can be located between the central port side streamer125 and the central starboard side streamer 130. The central port sidesource 150 can generate a source shot. The central port side source 150can generate acoustic waves. The central port side source 150 cangenerate acoustic waves to be reflected off a seabed object and receivedby the plurality of receivers 110. The central port side source 150 cangenerate acoustic waves to be diffracted off a seabed object andreceived by the plurality of receivers 110. The central starboard sidesource 155 can be located between the central port side streamer 125 andthe central starboard side streamer 130. The central starboard sidesource 155 can generate a source shot. The central starboard side source155 can generate acoustic waves. The central starboard side source 155can generate acoustic waves to be reflected off a seabed object andreceived by the plurality of receivers 110. The central starboard sidesource 155 can generate acoustic waves to be diffracted off a seabedobject and received by the plurality of receivers 110. The central portside source 150 can include a pair of sources. The central starboardside source 155 can include a pair of sources.

The source array 127 can include at least one auxiliary port side source160. The source array can include an auxiliary port side source 160. Theauxiliary port side source 160 can be located between the central portside streamer 125 and the auxiliary port side streamer 135. Theauxiliary port side source 160 can be located between a first auxiliaryport side streamer 135 and a second auxiliary port side streamer 135.The auxiliary port side source 160 can generate a source shot. Theauxiliary port side source 160 can generate acoustic waves. Theauxiliary port side source 160 can generate acoustic waves to bereflected off a seabed object and received by the plurality of receivers110. The auxiliary port side source 160 can generate acoustic waves tobe diffracted off a seabed object and received by the plurality ofreceivers 110. The source array 127 can include multiple auxiliary portside sources 160. For example, the source array 127 can include one,two, three, or more auxiliary port side sources 160. The auxiliary portside source 160 can include a pair of sources.

The source array 127 can include at least one auxiliary starboard sidesource 165. The auxiliary starboard side source 165 can be locatedbetween the central starboard side streamer 130 and the auxiliarystarboard side streamer 140. The auxiliary starboard side source 165 canbe located between a first auxiliary starboard side streamer 140 and asecond auxiliary starboard side streamer 140. The auxiliary starboardside source 165 can generate a source shot. The auxiliary starboard sidesource 165 can generate acoustic waves. The auxiliary starboard sidesource 165 can generate acoustic waves to be reflected off a seabedobject and received by the plurality of receivers 110. The auxiliarystarboard side source 165 can generate acoustic waves to be diffractedoff a seabed object and received by the plurality of receivers 110. Thesource array 127 can include multiple auxiliary starboard side source165. For example, the source array 127 can include one, two, three, ormore auxiliary starboard side source 165. The plurality of sources caninclude exactly eight sources. For example, the plurality of sources caninclude one central port side source 150, one central starboard sidesource 155, three auxiliary port side sources 160, and three auxiliarystarboard side sources 165. The auxiliary starboard side source 165 caninclude a pair of sources.

The seabed object detection system 100 can include a plurality of powercables 190. The power cable 190 can include an electrical cable totransmit electrical power. The power cable 190 can transmit electricalpower from the vessel 102 to the plurality of sources of the sourcearray 127. The power cable 190 can transmit electrical power from thevessel 102 to the central port side source 150. The power cable 190 cantransmit electrical power from the vessel 102 to the central starboardside source 155. The power cable 190 can transmit electrical power fromthe vessel 102 to the auxiliary port side source 160. The power cable190 can transmit electrical power from the vessel 102 to the auxiliarystarboard side source 165. The power cable 190 can transmit electricalpower from the vessel 102 to two sources of the central port side source150. The power cable 190 can transmit electrical power from the vessel102 to two sources of the central starboard side source 155. The powercable 190 can transmit electrical power from the vessel 102 to twosources of the auxiliary port side source 160. The power cable 190 cantransmit electrical power from the vessel 102 to two sources of theauxiliary starboard side source 165.

FIG. 8 illustrates a seabed object detection system 100. The seabedobject detection system 100 can include a source array 127 and areceiver array 105. The seabed object detection system 100 can includetwo sources of the source array 127 between receivers disposed on twostreamers of the plurality of streamers. The seabed object detectionsystem 100 can include a plurality of sample points 805. The samplepoint 805 can be located on the seabed 220. The source array 127 and thereceiver array 105 can be arranged in a pattern such at each samplepoint 805 is sampled four times.

FIG. 9 illustrates a method of seabed object detection according to anembodiment. In brief summary, the method 900 can include providing areceiver array (BLOCK 905). The method 900 can include providing asource array (BLOCK 910). The method 900 can include generating anacoustic signal (BLOCK 915). The method 900 can include receivingdiffraction data (BLOCK 920). The method 900 can include receivingreflection data (BLOCK 915).

The method 900 can include providing a receiver array (BLOCK 905). Themethod can include providing a providing a receiver array including aplurality of receivers. The plurality of receivers can receivediffraction data diffracted off an object in a seabed. The plurality ofreceivers can be disposed on a plurality of streamers. The plurality ofstreamers can include a central pair of streamers. The central pair ofstreamers can include a central port side streamer and a centralstarboard side streamer. The plurality of streamers can include at leastone auxiliary port side streamer located a first distance from thecentral pair of streamers. The plurality of streamers can include atleast one auxiliary starboard side streamer located a second distancefrom the central pair of streamers opposite the at least one auxiliaryport side streamer.

The method 900 can include providing a source array (BLOCK 910). Thesource array can include a plurality of sources. The plurality ofsources can generate a source shot. The plurality of sources can includeat least one central pair of sources. The at least one central pair ofsources can include a central port side source and a central starboardside source. The plurality of sources can be located between the centralpair of streamers. The source array can include at least one auxiliaryport side source. The at least one auxiliary port side source can belocated between the central port side streamer and the at least oneauxiliary port side streamer. The source array can include at least oneauxiliary starboard side source. The at least one auxiliary starboardside source can be located between the central starboard side streamerand the at least one auxiliary starboard side streamer.

In some embodiments, the method 900 can include disposing at least onereceiver of the plurality of receivers beyond a critical angle ofreflection for at least one source of the plurality of sources. The atleast one receiver can receive diffraction data responsive to anacoustic source. The critical angle can include a critical angle ofreflection. The critical angle can include a critical angle ofincidence. The critical angle of incidence is the angle at which arefracted wave travels along an interface between two media. A receiverof the plurality of receivers can be disposed beyond a critical angle ofreflection for a source of the source array. A receiver of the pluralityof receivers can be disposed beyond a critical angle of reflection for asource of the plurality of sources of the source array. The receiverdisposed beyond a critical angle of reflection can receive diffractiondata responsive to an acoustic source. The receiver disposed beyond acritical angle of reflection can receive diffraction data generated froma source shot. The source shot can generate acoustic waves. The receiverdisposed beyond a critical angle of reflection can receive diffractiondata generated from the acoustic waves.

The method 900 can include generating an acoustic signal (BLOCK 915).The method 900 can include generating, by the source array, an acousticsignal. The method can include generating, by the source array, acousticwaves. The acoustic waves can diffract off of the object in the seabed.The source array can generate acoustic waves. The acoustic waves caninclude a source shot. The acoustic waves can diffract off the object inthe seabed. The receiver array can receive diffracted waves originatingfrom the object in the seabed. The central pair of sources can generateacoustic waves. The central port side source can generate acousticwaves. The central starboard side source can generate acoustic waves.The auxiliary port side source can generate acoustic waves. Theauxiliary starboard side source can generate acoustic waves. A receiverof the plurality of receivers of the receiver array can receive thediffracted waves. A receiver disposed on the central port side streamercan receive the diffracted waves. A receiver disposed on the centralstarboard side streamer can receive the diffracted waves. A receiverdisposed on the auxiliary port side streamer can receive the diffractedwaves. A receiver disposed on the auxiliary starboard side streamer canreceive the diffracted waves.

In some embodiments, the method 900 can include towing, by a vessel, thereceiver array and the source array. The method can include towing, byvessel, the receiver array 15 meters to 50 meters above the seabed. Themethod can include towing, by the vessel, the source array ahead of thereceiver array. The vessel can tow the receiver array and the sourcearray such that the receiver array receives diffraction data diffractedoff an object in the seabed.

The method 900 can include receiving diffraction data (BLOCK 920). Themethod can include receiving, by the receiver array, diffraction datathat includes diffracted waves originating from a seabed object andgenerated from a source shot. The method can include receiving, by thereceiver array, diffraction data diffracted off the object in theseabed. The method can include receiving, by the receiver array,diffracted waves originating from the object in the seabed. Theplurality of receivers of the receiver array can receive diffractiondata. The diffraction data can include diffracted waves diffracted off aseabed object that is smaller than a Fresnel zone. The Fresnel zone isan area of a reflected from which most of the energy of a reflection isreturned and arrival times of the reflection differ by less than half aperiod from an arrival of energy propagated from an energy source. Waveswith such arrival times may interfere constructively and be detected bya single arrival. Therefore, detecting reflection waves from an objectsmaller than the Fresnel zone may be difficult. However, the pluralityof receivers 110 of the receiver array can detect diffracted waves froman object smaller than the Fresnel zone.

The method 900 can include receiving reflection data (BLOCK 915). Themethod can include receiving, by the receiver array, reflection datareflected off the object in the seabed. The source array can generate asource shot. The source shot can travel through a medium (e.g., seawater) and reflect off a seabed object. The seabed object can becompleted buried in the seabed. The seabed object can be partiallyburied in the seabed. The seabed object can include small shallowobjects such as boulders. The small shallow objects can be between 10 cmand 100 cm wide (e.g., 20 cm, 30 cm, 40 cm, 50 cm, 60 cm, 70 cm, 80 cm,90 cm, 100 cm). The small shallow objects can be greater than 100 cm.These small shallow objects can be less than 10 cm. The waves thatreflect off the seabed object may include reflection data. Thereflection data may include a reflected wave. The receiver array canreceive reflection data. For example, the receiver array can receive thereflected wave. A receiver of the plurality of receivers can receive thereflected wave. The reflection data can include a reflected waveoriginating from a seabed object. The reflection data can include thereflected wave generated from a source shot. The plurality of sources ofthe source array can generate an acoustic signal. The plurality ofreceivers of the receiver array can receive reflection data reflectedoff the object in the seabed. The reflection data can include areflected wave. A receiver of the plurality of receivers can receive thereflected wave reflected off the object in the seabed and generated by asource of the plurality of sources of the source array.

Embodiments of the subject matter and the operations described in thisspecification can be implemented in digital electronic circuitry, or incomputer software, firmware, or hardware, including the structuresdisclosed in this specification and their structural equivalents, or incombinations of one or more of them. The subject matter described inthis specification can be implemented as one or more computer programs,e.g., one or more circuits of computer program instructions, encoded onone or more computer storage media for execution by, or to control theoperation of, data processing apparatus. Alternatively or in addition,the program instructions can be encoded on an artificially generatedpropagated signal, e.g., a machine-generated electrical, optical, orelectromagnetic signal that is generated to encode information fortransmission to suitable receiver apparatus for execution by a dataprocessing apparatus. A computer storage medium can be, or be includedin, a computer-readable storage device, a computer-readable storagesubstrate, a random or serial access memory array or device, or acombination of one or more of them. Moreover, while a computer storagemedium is not a propagated signal, a computer storage medium can be asource or destination of computer program instructions encoded in anartificially generated propagated signal. The computer storage mediumcan also be, or be included in, one or more separate components or media(e.g., multiple CDs, disks, or other storage devices).

The operations described in this specification can be performed by adata processing apparatus on data stored on one or morecomputer-readable storage devices or received from other sources. Theterm “data processing apparatus” or “computing device” encompassesvarious apparatuses, devices, and machines for processing data,including by way of example a programmable processor, a computer, asystem on a chip, or multiple ones, or combinations of the foregoing.The apparatus can include special purpose logic circuitry, e.g., an FPGA(field programmable gate array) or an ASIC (application specificintegrated circuit). The apparatus can also include, in addition tohardware, code that creates an execution environment for the computerprogram in question, e.g., code that constitutes processor firmware, aprotocol stack, a database management system, an operating system, across-platform runtime environment, a virtual machine, or a combinationof one or more of them. The apparatus and execution environment canrealize various different computing model infrastructures, such as webservices, distributed computing and grid computing infrastructures.

A computer program (also known as a program, software, softwareapplication, script, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, declarative orprocedural languages, and it can be deployed in any form, including as astand-alone program or as a circuit, component, subroutine, object, orother unit suitable for use in a computing environment. A computerprogram may, but need not, correspond to a file in a file system. Aprogram can be stored in a portion of a file that holds other programsor data (e.g., one or more scripts stored in a markup languagedocument), in a single file dedicated to the program in question, or inmultiple coordinated files (e.g., files that store one or more circuits,subprograms, or portions of code). A computer program can be deployed tobe executed on one computer or on multiple computers that are located atone site or distributed across multiple sites and interconnected by acommunication network.

Processors suitable for the execution of a computer program include, byway of example, microprocessors, and any one or more processors of adigital computer. A processor can receive instructions and data from aread only memory or a random access memory or both. The elements of acomputer are a processor for performing actions in accordance withinstructions and one or more memory devices for storing instructions anddata. A computer can include, or be operatively coupled to receive datafrom or transfer data to, or both, one or more mass storage devices forstoring data, e.g., magnetic, magneto optical disks, or optical disks. Acomputer need not have such devices. Moreover, a computer can beembedded in another device, e.g., a personal digital assistant (PDA), aGlobal Positioning System (GPS) receiver, or a portable storage device(e.g., a universal serial bus (USB) flash drive), to name just a few.Devices suitable for storing computer program instructions and datainclude all forms of non-volatile memory, media and memory devices,including by way of example semiconductor memory devices, e.g., EPROM,EEPROM, and flash memory devices; magnetic disks, e.g., internal harddisks or removable disks; magneto optical disks; and CD ROM and DVD-ROMdisks. The processor and the memory can be supplemented by, orincorporated in, special purpose logic circuitry.

To provide for interaction with a user, implementations of the subjectmatter described in this specification can be implemented on a computerhaving a display device, e.g., a CRT (cathode ray tube) or LCD (liquidcrystal display) monitor, for displaying information to the user and akeyboard and a pointing device, e.g., a mouse or a trackball, by whichthe user can provide input to the computer. Other kinds of devices canbe used to provide for interaction with a user as well; for example,feedback provided to the user can be any form of sensory feedback, e.g.,visual feedback, auditory feedback, or tactile feedback; and input fromthe user can be received in any form, including acoustic, speech, ortactile input.

The implementations described herein can be implemented in any ofnumerous ways including, for example, using hardware, software or acombination thereof. When implemented in software, the software code canbe executed on any suitable processor or collection of processors,whether provided in a single computer or distributed among multiplecomputers.

Also, a computer may have one or more input and output devices. Thesedevices can be used, among other things, to present a user interface.Examples of output devices that can be used to provide a user interfaceinclude printers or display screens for visual presentation of outputand speakers or other sound generating devices for audible presentationof output. Examples of input devices that can be used for a userinterface include keyboards, and pointing devices, such as mice, touchpads, and digitizing tablets. As another example, a computer may receiveinput information through speech recognition or in other audible format.

Such computers may be interconnected by one or more networks in anysuitable form, including a local area network or a wide area network,such as an enterprise network, and intelligent network (IN) or theInternet. Such networks may be based on any suitable technology and mayoperate according to any suitable protocol and may include wirelessnetworks, wired networks or fiber optic networks.

A computer employed to implement at least a portion of the functionalitydescribed herein may comprise a memory, one or more processing units(also referred to herein simply as “processors”), one or morecommunication interfaces, one or more display units, and one or moreuser input devices. The memory may comprise any computer-readable media,and may store computer instructions (also referred to herein as“processor-executable instructions”) for implementing the variousfunctionalities described herein. The processing unit(s) may be used toexecute the instructions. The communication interface(s) may be coupledto a wired or wireless network, bus, or other communication means andmay therefore allow the computer to transmit communications to orreceive communications from other devices. The display unit(s) may beprovided, for example, to allow a user to view various information inconnection with execution of the instructions. The user input device(s)may be provided, for example, to allow the user to make manualadjustments, make selections, enter data or various other information,or interact in any of a variety of manners with the processor duringexecution of the instructions.

The various methods or processes outlined herein may be coded assoftware that is executable on one or more processors that employ anyone of a variety of operating systems or platforms. Additionally, suchsoftware may be written using any of a number of suitable programminglanguages or programming or scripting tools, and also may be compiled asexecutable machine language code or intermediate code that is executedon a framework or virtual machine.

In this respect, various inventive concepts may be embodied as acomputer readable storage medium (or multiple computer readable storagemedia) (e.g., a computer memory, one or more floppy discs, compactdiscs, optical discs, magnetic tapes, flash memories, circuitconfigurations in Field Programmable Gate Arrays or other semiconductordevices, or other non-transitory medium or tangible computer storagemedium) encoded with one or more programs that, when executed on one ormore computers or other processors, perform methods that implement thevarious embodiments of the solution discussed above. The computerreadable medium or media can be transportable, such that the program orprograms stored thereon can be loaded onto one or more differentcomputers or other processors to implement various aspects of thepresent solution as discussed above.

The terms “program” or “software” are used herein to refer to any typeof computer code or set of computer-executable instructions that can beemployed to program a computer or other processor to implement variousaspects of embodiments as discussed above. One or more computer programsthat when executed perform methods of the present solution need notreside on a single computer or processor, but may be distributed in amodular fashion amongst a number of different computers or processors toimplement various aspects of the present solution.

Computer-executable instructions may be in many forms, such as programmodules, executed by one or more computers or other devices. Programmodules can include routines, programs, objects, components, datastructures, or other components that perform particular tasks orimplement particular abstract data types. The functionality of theprogram modules can be combined or distributed as desired in variousembodiments.

Also, data structures may be stored in computer-readable media in anysuitable form. For simplicity of illustration, data structures may beshown to have fields that are related through location in the datastructure. Such relationships may likewise be achieved by assigningstorage for the fields with locations in a computer-readable medium thatconvey relationship between the fields. However, any suitable mechanismmay be used to establish a relationship between information in fields ofa data structure, including through the use of pointers, tags or othermechanisms that establish relationship between data elements.

Any references to implementations or elements or acts of the systems andmethods herein referred to in the singular can include implementationsincluding a plurality of these elements, and any references in plural toany implementation or element or act herein can include implementationsincluding only a single element. References in the singular or pluralform are not intended to limit the presently disclosed systems ormethods, their components, acts, or elements to single or pluralconfigurations. References to any act or element being based on anyinformation, act or element may include implementations where the act orelement is based at least in part on any information, act, or element.

Any implementation disclosed herein may be combined with any otherimplementation, and references to “an implementation,” “someimplementations,” “an alternate implementation,” “variousimplementations,” “one implementation” or the like are not necessarilymutually exclusive and are intended to indicate that a particularfeature, structure, or characteristic described in connection with theimplementation may be included in at least one implementation. Suchterms as used herein are not necessarily all referring to the sameimplementation. Any implementation may be combined with any otherimplementation, inclusively or exclusively, in any manner consistentwith the aspects and implementations disclosed herein.

References to “or” may be construed as inclusive so that any termsdescribed using “or” may indicate any of a single, more than one, andall of the described terms. References to at least one of a conjunctivelist of terms may be construed as an inclusive OR to indicate any of asingle, more than one, and all of the described terms. A reference to“at least one of ‘A’ and ‘B’” can include only ‘A’, only ‘B’, as well asboth ‘A’ and ‘B’. Elements other than ‘A’ and ‘B’ can also be included.

The systems and methods described herein may be embodied in otherspecific forms without departing from the characteristics thereof. Theforegoing implementations are illustrative rather than limiting of thedescribed systems and methods.

Where technical features in the drawings, detailed description or anyclaim are followed by reference signs, the reference signs have beenincluded to increase the intelligibility of the drawings, detaileddescription, and claims. Accordingly, neither the reference signs northeir absence have any limiting effect on the scope of any claimelements.

The systems and methods described herein may be embodied in otherspecific forms without departing from the characteristics thereof. Theforegoing implementations are illustrative rather than limiting of thedescribed systems and methods. Scope of the systems and methodsdescribed herein is thus indicated by the appended claims, rather thanthe foregoing description, and changes that come within the meaning andrange of equivalency of the claims are embraced therein.

1.-20. (canceled)
 21. A seabed object detection system, comprising: astreamer array including at least one streamer; a receiver arrayincluding at least one receiver, the at least one receiver disposed onthe at least one streamer and the at least one receiver to receivediffraction data, the diffraction data indicative of acoustic wavesdiffracted off an object in a seabed; a source array including at leastone source; the at least one receiver disposed beyond a critical angleof reflection for the at least one source, the at least one receiver toreceive the diffraction data responsive to an acoustic source; and thecritical angle of reflection defined by an angle at which a refractedwave from the acoustic source travels along an interface between theseabed and seawater.
 22. The seabed object detection system of claim 21,wherein: the at least one source comprises at least one central pair ofsources, the at least one central pair of sources including a centralport side source and a central starboard side source.
 23. The seabedobject detection system of claim 21, wherein: the at least one streamercomprises a central pair of streamers, the central pair of streamersincluding a central port side streamer and a central starboard sidestreamer.
 24. The seabed object detection system of claim 21, wherein:the at least one streamer comprises a central pair of streamers, thecentral pair of streamers including a central port side streamer and acentral starboard side streamer; the at least one source comprises atleast one central pair of sources, the at least one central pair ofsources including a central port side source and a central starboardside source; and the at least one central pair of sources disposedbetween the central pair of streamers.
 25. The seabed object detectionsystem of claim 21, wherein: the at least one streamer comprises: acentral pair of streamers, the central pair of streamers including acentral port side streamer and a central starboard side streamer; atleast one auxiliary port side streamer located a first distance from thecentral pair of streamers; and at least one auxiliary starboard sidestreamer located a second distance from the central pair of streamersopposite the at least one auxiliary port side streamer.
 26. The seabedobject detection system of claim 21, wherein: the at least one sourcecomprises: at least one central pair of sources, the at least onecentral pair of sources including a central port side source and acentral starboard side source; at least one auxiliary port side source;and at least one auxiliary starboard side source.
 27. The seabed objectdetection system of claim 21, wherein: the at least one streamercomprises: a central pair of streamers, the central pair of streamersincluding a central port side streamer and a central starboard sidestreamer; at least one auxiliary port side streamer located a firstdistance from the central pair of streamers; and at least one auxiliarystarboard side streamer located a second distance from the central pairof streamers opposite the at least one auxiliary port side streamer; andthe at least one source comprises: at least one central pair of sources,the at least one central pair of sources including a central port sidesource and a central starboard side source; at least one auxiliary portside source located between the central port side streamer and the atleast one auxiliary port side streamer; and at least one auxiliarystarboard side source located between the central starboard sidestreamer and the at least one auxiliary starboard side streamer.
 28. Theseabed object detection system of claim 21, comprising: the at least onereceiver to receive diffraction data diffracted off the object that issmaller than a Fresnel zone.
 29. The seabed object detection system ofclaim 21, comprising: the receiver array to receive diffraction datathat includes diffracted waves originating from the object in theseabed.
 30. The seabed object detection system of claim 21, comprising:a vessel configured to tow the receiver array and the source array, thesource array to generate an acoustic signal and the receiver array toreceive diffraction data diffracted off the object in the seabed. 31.The seabed object detection system of claim 21, comprising: the sourcearray to generate acoustic waves, the acoustic waves to diffract off ofthe object in the seabed; and the receiver array to receive diffractedwaves originating from the object in the seabed.
 32. A method of seabedobject detection, comprising: providing a streamer array including atleast one streamer; providing a receiver array including at least onereceiver, the at least one receiver disposed on the at least onestreamer and the at least one receiver to receive diffraction data, thediffraction data indicative of acoustic waves diffracted off a seabedobject; providing a source array including at least one source;disposing the at least one receiver beyond a critical angle ofreflection for the at least one source, the at least one receiver toreceive diffraction data responsive to an acoustic source, the criticalangle of reflection defined at least in part by an angle at which arefracted wave from the acoustic source travels along an interfacebetween a seabed and seawater.
 33. The method of claim 32, comprising:providing at least one central pair of sources, the at least one centralpair of sources including a central port side source and a centralstarboard side source.
 34. The method of claim 32, comprising: providinga central pair of streamers, the central pair of streamers including acentral port side streamer and a central starboard side streamer. 35.The method of claim 32, comprising: providing a central pair ofstreamers, the central pair of streamers including a central port sidestreamer and a central starboard side streamer; providing at least onecentral pair of sources, the at least one central pair of sourcesincluding a central port side source and a central starboard sidesource; and disposing the at least one central pair of sources betweenthe central pair of streamers.
 36. The method of claim 32, comprising:providing a central pair of streamers, the central pair of streamersincluding a central port side streamer and a central starboard sidestreamer; locating at least one auxiliary port side streamer a firstdistance from the central pair of streamers; and locating at least oneauxiliary starboard side streamer a second distance from the centralpair of streamers opposite the at least one auxiliary port sidestreamer.
 37. The method of claim 32, comprising: providing at least onecentral pair of sources, the at least one central pair of sourcesincluding a central port side source and a central starboard sidesource; providing at least one auxiliary port side source; and providingat least one auxiliary starboard side source.
 38. The method of claim32, comprising: providing a central pair of streamers, the central pairof streamers including a central port side streamer and a centralstarboard side streamer; locating at least one auxiliary port sidestreamer a first distance from the central pair of streamers; locatingat least one auxiliary starboard side streamer a second distance fromthe central pair of streamers opposite the at least one auxiliary portside streamer; providing at least one central pair of sources, the atleast one central pair of sources including a central port side sourceand a central starboard side source; locating at least one auxiliaryport side source between the central port side streamer and the at leastone auxiliary port side streamer; and locating at least one auxiliarystarboard side source between the central starboard side streamer andthe at least one auxiliary starboard side streamer.
 39. The method ofclaim 32, comprising: receiving, by the receiver array, diffraction datathat includes diffracted waves originating from an object in the seabed.40. The method of claim 32, comprising: towing, by a vessel, thereceiver array and the source array; generating, by the source array, anacoustic signal; and receiving, by the receiver array, diffraction datadiffracted off an object in the seabed.